CN113468835A - Electromagnetic interference prediction software for BUCK chopper - Google Patents
Electromagnetic interference prediction software for BUCK chopper Download PDFInfo
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Abstract
The invention discloses electromagnetic interference prediction software of a BUCK chopper, which simplifies parasitic parameters of a BUCK chopper circuit based on the idea of giant-variation sensitivity; using Simulink to build a simulation model to express the simplified chopper circuit; performing data interaction and data processing by using a GUI (graphical user interface) and a Simulink module of MATLAB software to obtain circuit simulation results under various conditions; the prediction software has comprehensive functions, is convenient to research and develop, and design and production personnel can quickly master the approximate common-mode interference time domain waveform and frequency spectrum of the circuit, and can predict the common-mode interference even if different switching device control signals and different circuit performance indexes (output voltage amplitude, edge gradient of switching device action and the like) exist. The chopper test system provides convenience for production design, interference test and the like of the chopper.
Description
Technical Field
The invention particularly relates to electromagnetic interference prediction software of a BUCK chopper.
Background
Nowadays, the electromagnetic interference problem is increasingly concerned, and a chopper with a high-frequency switching device needs to be convenient and accurate for electromagnetic interference prediction.
The invention discloses electromagnetic interference prediction software of a BUCK chopper, which simplifies parasitic parameters of a BUCK chopper circuit based on the idea of giant-variation sensitivity; using Simulink to build a simulation model to express the simplified chopper circuit; performing data interaction and data processing by using a GUI (graphical user interface) and a Simulink module of MATLAB software to obtain circuit simulation results under various conditions; the prediction software has comprehensive functions, is convenient to research and develop, and design and production personnel can quickly master the approximate common-mode interference time domain waveform and frequency spectrum of the circuit, and can predict the common-mode interference even if different switching device control signals and different circuit performance indexes (output voltage amplitude, edge gradient of switching device action and the like) exist. The chopper test system provides convenience for production design, interference test and the like of the chopper.
Disclosure of Invention
The technical problem to be solved by the invention is to overcome the defects of the technology, and the invention provides:
an electromagnetic interference prediction software of a BUCK chopper,
selecting and determining a simulation interference model corresponding to the interference source model through interlocked radio buttons;
acquiring a simulation file according to the selected simulation interference model;
if the acquisition of the simulation file fails, an error is reported, and the program is terminated;
if the simulation file is successfully acquired, loading the file for pre-operation; determining a conduction path for distinguishing choppers of different models by inputting parasitic parameters respectively corresponding to element data in the simulation interference model;
setting circuit performance index data corresponding to the chopper in the previous step, wherein the circuit performance index data correspond to different simulation interference models and present different parameters;
judging whether the input circuit performance index data meets the general rule of the corresponding simulation interference model, if not, the data is abnormal, and executing re-input;
if the data are in accordance with the set _ param function, the data are normal, and the data are correspondingly written into the simulation file through the set _ param function and the simulation is run;
displaying a time domain image and a frequency domain image of the predicted common-mode interference voltage through the common-mode interference amplitude value, the maximum value and the resonance point of the target chopper in the simulation result;
if the data needs to be changed for a plurality of times of experiments, re-input is executed, and if the program needs to be ended, a termination program is executed.
As an improvement, the simulation interference model has three types, including a square wave, a Pulse Width Modulation (PWM) wave capable of changing duty ratio and a trapezoidal wave capable of changing edge gradient; the simulation interference model consists of basic circuit elements and control signals; the basic circuit elements comprise a resistor, an inductor, a capacitor and an ideal voltage source; the ideal voltage source is used for simulating an actual interference source, namely a circuit output end controlled by a switching device IGBT in the chopper circuit; and the control signal waveform is built through a signal generation module.
As a refinement, the parasitic parameters include R, L, C, where R represents the resistance of the impedance stabilization network, L represents the parallel value of the positive and negative bus inductances, and C represents the IGBT parasitic capacitance to ground.
As an improvement, the calculation formula of the positive and negative bus inductance parallel value L is as follows:
wherein l is the length, w is the width, and t is the height.
As an improvement, the calculation formula of the IGBT parasitic capacitance to ground C is:
C＝ε0εγA/d，
wherein A is the surface area and d is the width.
As an improvement, in the simulation interference model under the square wave control, a square wave generator Signal generator is adopted to control a voltage source; the adjustable circuit performance index data comprises voltage amplitude and waveform frequency, and the steepness of the edge of the IGBT is invariably infinite.
As an improvement, in the simulation interference model under the control of the PWM wave, the on-time is changed under the condition that the waveform period is inconvenient; the PWM control signal is modulated by a triangular carrier and a Constant module Constant, and a control signal is output to a voltage source by comparing the triangular carrier and the Constant module Constant; the duty ratio of the output waveform of the voltage source is changed by changing the amplitude of the constant module; multiplying the output voltage amplitude and the output result of the comparison unit to change the output amplitude of the interference source; the adjustable circuit performance index data comprise voltage amplitude, frequency and duty ratio and are used for researching the influence of the duty ratio of the circuit switching device control signal on common-mode interference voltage.
As an improvement, in the simulation interference model under the control of the trapezoidal wave, the generation of the waveform is completed through a Repeating Sequence module, and the modification of the steepness of the rising edge or the falling edge is realized; the adjustable circuit performance index data comprises a voltage amplitude, a waveform frequency and IGBT edge steepness.
As an improvement, obtaining data of the time domain signal through a measuring instrument and a system clock of common mode voltage on an LISN resistor of a simulation interference model; the frequency domain data is obtained by processing the time domain signal through Fourier transform.
Compared with the prior art, the invention has the advantages that: the invention effectively combines the electromagnetic interference path and the interference source model with the actual chopper circuit modeling based on the Simulink simulation module and the GUIDE image interface module of MATLAB, realizes the prediction of various interference types aiming at different models of BUCK choppers, and has adjustable circuit performance parameters. Based on the drawn common-mode voltage interference spectrogram, a user can visually know important information such as a common-mode interference amplitude value, a maximum value, a resonance point and the like of the target chopper.
Drawings
FIG. 1 is a flow chart of the electromagnetic interference prediction software of the BUCK chopper.
FIG. 2 is a simulation model of the chopper in the electromagnetic interference prediction software of the BUCK chopper.
FIG. 3 is a GUI interface in the electromagnetic interference prediction software of the BUCK chopper of the present invention.
FIG. 4 is a Simulink interface in the electromagnetic interference prediction software of the BUCK chopper of the present invention.
Fig. 5 is a voltage source square wave control signal behavior.
Fig. 6 is a voltage source PWM wave control signal operation.
Fig. 7 is a voltage source trapezoidal wave control signal operating condition.
Fig. 8 is a square wave spectral prediction waveform.
Fig. 9 is a real experiment common mode voltage spectrum.
FIG. 10 is a comparison of the magnitude voltage spectrum.
Detailed Description
The following describes a BUCK chopper electromagnetic interference prediction software in further detail with reference to the accompanying drawings.
Referring to the attached drawings, FIGS. 1 to 10 show electromagnetic interference prediction software for a BUCK chopper,
selecting and determining a simulation interference model corresponding to the interference source model through interlocked radio buttons;
acquiring a simulation file according to the selected simulation interference model;
if the acquisition of the simulation file fails, an error is reported, and the program is terminated;
if the simulation file is successfully acquired, loading the file for pre-operation; determining a conduction path for distinguishing choppers of different models by inputting parasitic parameters respectively corresponding to element data in the simulation interference model;
setting circuit performance index data corresponding to the chopper in the previous step, wherein the circuit performance index data correspond to different simulation interference models and show different parameters;
judging whether the input circuit performance index data meets the general rule of the corresponding simulation interference model, if not, the data is abnormal, and executing re-input;
if the data are in accordance with the set _ param function, the data are normal, and the data are correspondingly written into the simulation file through the set _ param function and the simulation is run;
displaying a time domain image and a frequency domain image of the predicted common-mode interference voltage through the common-mode interference amplitude value, the maximum value and the resonance point of the target chopper in the simulation result;
if the data needs to be changed for a plurality of times of experiments, re-input is executed, and if the program needs to be ended, a termination program is executed.
In the embodiment, the simulation interference model has three types, including a square wave, a Pulse Width Modulation (PWM) wave capable of changing duty ratio and a trapezoidal wave capable of changing edge gradient; the simulation interference model consists of basic circuit elements and control signals; the basic circuit elements comprise a resistor, an inductor, a capacitor and an ideal voltage source; the ideal voltage source is used for simulating an actual interference source, namely a circuit output end controlled by a switching device IGBT in the chopper circuit; the control signal waveform is built through the signal generating module.
In this embodiment, the parasitic parameters include R, L, C, where R represents the resistance of the impedance stabilization network, L represents the parallel value of the positive and negative bus inductances, and C represents the parasitic capacitance of the IGBT to ground.
In this embodiment, a calculation formula of the positive and negative bus inductance parallel value L is:
wherein l is the length, w is the width, and t is the height.
In this embodiment, the calculation formula of the IGBT to ground parasitic capacitance C is:
C＝ε0εγA/d，
wherein A is the surface area and d is the width.
In the embodiment, in a simulation interference model under square wave control, a square wave generator Signal generator is adopted to control a voltage source; the adjustable circuit performance index data comprises voltage amplitude and waveform frequency, and the steepness of the edge of the IGBT is invariably infinite.
In the embodiment, in a simulation interference model under the control of a PWM (pulse-width modulation) wave, the opening time is changed under the condition of inconvenient waveform period; the PWM control signal is modulated by a triangular carrier and a Constant module Constant, and a control signal is output to a voltage source by comparing the triangular carrier and the Constant module Constant; the duty ratio of the output waveform of the voltage source is changed by changing the amplitude of the constant module; multiplying the output voltage amplitude and the output result of the comparison unit to change the output amplitude of the interference source; the adjustable circuit performance index data comprises voltage amplitude, frequency and duty ratio and is used for researching the influence of the duty ratio of the control signal of the circuit switching device on the common-mode interference voltage.
In this embodiment, in the simulated interference model under the control of the trapezoidal wave, the generation of the waveform is completed through the Repeating Sequence of the cyclic Sequence module, and the modification of the steepness of the rising edge or the falling edge is realized; the adjustable circuit performance index data comprises voltage amplitude, waveform frequency and IGBT edge steepness.
In the embodiment, time domain signal data is obtained through a measuring instrument and a system clock of common mode voltage on an LISN resistor of a simulation interference model; the frequency domain data is obtained by processing the time domain signal through Fourier transform.
The software execution mode of the invention is explained as follows: and ensuring MATLAB software in a computer, decompressing the ZIP packet, modifying the file path in the bat file to be the path of the current file, and double-clicking the MATLAB GUI.
Description of the use of the software in the invention:
1) the user selects the type of the software interference source and the software interference source is divided into three conditions: if the duty ratio of the researched circuit is not changed, the square wave signal is selected, if the duty ratio of the researched circuit is changed, the PWM waveform is selected, and if the high-frequency signal with the frequency band higher than 10MHz needs to be researched, the trapezoidal wave is selected. After the selection is finished, the confirmation setting button is clicked, and the software loads the corresponding interference model into the working space. Note that: no modification is allowed after the selection of the interference source type is completed,
2) and (3) modifying the interference path parameters on a GUI (graphical user interface) of the electromagnetic interference prediction software of the chopper circuit by a user, wherein R: the resistance of the impedance stabilizing network, L, the parallel connection value of positive and negative bus inductors, C, the parasitic capacitance of the IGBT to the ground, and the software stores parameters.
3) The chopper performance parameters are filled in, and the modules differ slightly depending on the type of disturbance selected. If square waves are selected, only the voltage amplitude is needed, the waveform frequency is adjustable, and the steepness of the edge of the IGBT is invariably infinite; if the PWM wave is selected, the voltage amplitude, the frequency and the duty ratio are adjustable, and the method is used for researching the influence of the duty ratio of a control signal of a circuit switching device on the common-mode interference voltage; if the trapezoidal wave is selected, the voltage amplitude, the waveform frequency and the IGBT edge steepness can be adjusted, however, the frequency and the steepness need to be set according to an objective rule, if the slope parameter of the IGBT edge is far lower than the switching frequency, an extreme condition that the time domain waveform period is shorter than the time required by the rising edge may occur, and the interface throws out an exception and prompts a user to input the exception again.
4) If the chopper parameter panel is to be hidden, the finish button can be clicked. If the panel needs to be called out, a chopper parameter setting button is clicked.
5) If all the settings are finished, the software displays time domain waveforms and frequency domain waveforms on the upper and lower axis controls respectively by clicking the operation button. The amplitude of the circuit common mode electromagnetic interference, the trend of the change along with the frequency and other information can be definitely obtained in the prediction software in the PWM mode.
The prediction software is developed by an MATLAB tool, and simultaneously runs GUIDE and Simulink. The flow outline of the program execution is as follows:
first, the control signals of the IGBTs are different, and the models of the interference sources are also different, so that the simulation circuits are also different. Therefore, firstly, the required interference source is selected under the GUI interface; secondly, determining an operating Simulink simulation model according to the selection on a GUI interface; then receiving parameters to be modified such as parasitic parameters, voltage amplitudes and the like from the GUI interface, and correspondingly modifying the parameters of the simulation model through a set _ param function; and finally, operating a simulation model, simultaneously acquiring the output amplitude of the time and the interference voltage from the Simulink model, and storing the output amplitude of the time and the output amplitude of the interference voltage into a working space of the GUI for drawing and displaying. The software flow diagram of the present invention is shown in fig. 1.
GUI interface As shown in FIG. 3, the interface can be divided into three parts, a display part, a data input part and a control part. The GUI interfaces use controls for image axes, buttons, radio buttons, panels, editable text, and static text, respectively.
The GUI data input part can be divided into three input intervals according to different supported functions, and a user needs to set parameters of each input control according to own requirements. First, parasitic parameter input area: r, L, C, inputting parameters which respectively correspond to element data in a Simulink simulation model, and determining a conduction path to distinguish choppers of different models; second, the interferer model selects the region: the method comprises the following steps that interlocked radio buttons are used for respectively representing different Simulink simulation files, three interference models, namely a pulse width modulation wave with a square wave and a duty ratio changeable and a trapezoidal wave with an edge gradient changeable are available, wherein the trapezoidal wave interference source model is suitable for the condition that the interference frequency band to be researched is higher than 10 MHz; third, the circuit performance index setting area: the editable text boxes embedded in the panels correspond to performance indexes such as the amplitude of the output voltage, the switching frequency and the edge gradient of the chopper and present different parameters corresponding to different interference models.
The GUI control part completes functions of data processing, man-machine interaction and the like, and comprises a plurality of button controls which are used for confirming parameter change, displaying an input area of the hidden part, controlling the running of software and the like. Button controls of a GUI often implement control functions using callback functions. For example, the callback function of the "parameter ok" button automatically saves GUI interface data to internal variables and passes the data through global variables to each button control. And the 'operation' button callback function writes the data of the control acquired by the tag label of each text box into a corresponding element of the simulation model, so as to complete model operation and data processing.
The GUI display part consists of an upper image axis and a lower image axis and is used for displaying the waveforms of a time domain and a frequency domain respectively. The data of the time domain signals are from a measuring instrument and a system clock of common-mode voltage on an LISN resistor of the simulation model, and the frequency domain data are obtained by processing the time domain signals through Fourier transform. According to the frequency domain signal characteristics, the vertical axis is set to a decibel form and the horizontal axis is set to a logarithmic form in the EMC.
In order to make different interference source types available in the process of GUI software, different interference source simulation models need to be built on the simulation interface. Therefore, the Simulink models of which the voltage source signal ends are square waves, PWM waves and trapezoidal waves are respectively constructed. The simulation model is composed of basic circuit elements and control signals. The basic circuit elements of the simulation model are built according to the chopper simulation model shown in FIG. 2, and are simplified by using the idea of giant sensitivity, and the basic circuit elements of each model are the same. The control signal waveform is built up by the signal generation module, as will be described in detail below.
The basic circuit elements are composed of resistance, inductance, capacitance elements and ideal voltage sources, and simulate actual electromagnetic compatibility interference paths and parasitic parameters in interference coupling paths. The voltage source has the function of simulating an actual interference source, namely the circuit output controlled by the switching device IGBT in the chopper circuit. The resistor actually simulates an impedance stabilization network LISN in the detection circuit and plays a role in receiving electromagnetic interference energy, so that common-mode interference voltage can be obtained by measuring voltages at two ends of the resistor, and then data is output by an output single block (output single block).
Fig. 4 shows an interface in the case of PWM modulation, and the control signal of the simulation circuit is a PWM wave, in order to change the duty ratio and study the influence of the control signal duty ratio of the interference source on the electromagnetic interference. The chopper PWM control principle is that under the condition of unchanging waveform period, the turn-on time is changed. In the prediction software, the PWM control signal is modulated by a triangular carrier and a Constant module Constant, and the control signal is output to the voltage source through comparison of the triangular carrier and the Constant module Constant. And the duty ratio of the output waveform of the voltage source is changed by changing the amplitude of the constant module. And multiplying the output voltage amplitude with the output result of the comparison unit to change the output amplitude of the interference source.
The interference source model under the chopper square wave control Signal directly uses a square wave generator control voltage source because the duty ratio does not need to be changed. Trapezoidal waves or the need to modify the rising/falling edge steepness, while Simulink does not have a module for generating this waveform directly, so a cyclic Sequence module (Repeating Sequence) is considered.
According to the method, a time domain waveform is obtained by a simulation model, then a corresponding frequency domain graph is obtained by calculating the time domain graph through a Fourier transform formula, and finally the frequency domain graph is displayed in a GUI interface in a centralized mode.
The MATLAB supports the function of controlling the simulation state through a function, can load and store a simulation model, sets a simulation option to run from the current working space, runs the specified simulation model by applying a sim function, and stops the simulation model by setting a simulation command parameter, thereby achieving the purpose of controlling the running and stopping of the simulation model from the current working space.
load_system(handles_open_model)；
options＝simset('SrcWorkspace','current')；
sim(handles_open_model,[],options)；
set_param(handles_open_model,'SimulationCommand','stop')
save_system(handles_open_model)；
In order to directly call the output data obtained by simulation in the GUI, the simulation output data needs to be saved to a working space. The simulation model built in Simulink is shown in FIG. 4. The output clock data is automatically generated by a simulation model, and the time domain common mode interference amplitude is obtained by measuring the voltages at two ends of the LISN resistor.
The measured voltage is connected to an output module, a model configuration parameters-data input/output is set, an output clock tout and an output amplitude yout are selected, and a proper number of sampling points is set to ensure the precision. It can be found that tout and yout parameters appear in the workspace interface of the MATLAB, indicating that the operation of loading the acquired time-domain simulation data into the workspace has been completed.
In order to acquire the frequency domain waveform, fourier transform is needed to transform the time domain data in the working space into a spectrogram and display the image result. The sampling time and the frequency of each point can be obtained through simple calculation and taken as the horizontal axis of a spectrogram, fft function is used for carrying out fast Fourier transform on the output amplitude, and then the result is logarithmized by taking 10 as a base number and taken as the vertical axis.
In order to display an image, the axes function carried by the GUI module is required to be used for specifying a shaft control element bearing the image, and then a drawing function can be normally called to realize image display. In order to enlarge the spectrum display range, the output frequency domain axis needs to be changed into logarithmic coordinates, a figure window is popped up by using a figure function, the scale of the horizontal axis is changed into logarithm in an attribute editor, and the range of the horizontal axis is 105-108。
n ═ length (tout); % n sample time, data points
f ═ 1: n × 100000000/n; % frequency of nth point, 100000000 is the sampling frequency.
Fft (yout); % Fourier transform
mag ═ abs (y); % amplitude
yy＝20*log10(mag)+60；
axes(handles.axes3)
figure ('Name', 'common mode spectrogram');
plot(f(1:n/2),yy(1:n/2))
the R, L, C element parameters in the simulation model are obtained from the simulation simplest circuit diagram. External uncontrollable environmental factors, the material processing of electronic devices, may affect parasitic parameters of the emc circuit. Therefore, the user is indispensable for adapting the function of the parameter of the chopper to be tested in the current test environment by modifying the relevant parameter.
The function that the software needs to complete is that in actual operation, after the chopper parameters obtained through actual measurement are correspondingly filled in R, L, C element parameter text boxes in a GUI interface, the element parameters of the corresponding simulation model can be automatically modified, and correct time domain and frequency domain waveforms are output. Taking LISN resistance as an example, the code is implemented as follows:
setting initial values of GUI controls
R_init＝'25'；
set(handles.edit2,'String',R_init)；
Obtaining text control parameters of GUI interface
R＝get(handles.edit2,'String')；
Command line acquisition target component parameter name
find_system('diancimodel','Type','BLOCK')
get_param('diancimodel/ParallelRLCBranch','DialogParameters')
Setting element parameters of simulation model
set_param('diancimodel/ParallelRLCBranch','Resistance',R)
The idea of developing the interference source type setting is to establish different simulation models according to the interference source type, obtain the selection of a user through a GUI interface, and finally modify and simulate the element parameters of the selected interference source to obtain a frequency spectrum result. The selection of the corresponding simulation circuit by the type of the interference source is the key of the function. The code is implemented as follows:
three radio boxes are added, and the interlocking function is added respectively.
function radiobutton1_Callback(hObject,eventdata,handles)
set(handles.radiobutton1,'value',1)；
set(handles.radiobutton2,'value',0)；
set(handles.radiobutton3,'value',0)；
And defining the global variable of the simulation model, and judging the operated model according to the value of the radio box.
The global variables are used to control the running and stopping of the simulation.
Before modifying the simulation model parameters, the if statement is used for model judgment, and the element parameters of the selected model are modified.
Setting the output amplitude and frequency of the square wave interference voltage source:
the output amplitude of the chopper circuit determines the amplitude of the common-mode interference voltage, so that the amplitude of the circuit output voltage needs to be considered in addition to the influence of circuit parameters on the transmission interference. Similar to modifying R, L, C parameters, the modification of the output amplitude of the chopper circuit also requires the corresponding modification of the parameters of the elements in the simulation model. Since the output waveform of the controlled voltage Source module (Simulink) is completely the same as the waveform of the control end, it is considered to use the product module to boost the amplitude before the waveform is input into the control end. The purpose of controlling the amplitude of the output voltage can be achieved by modifying the parameters of the module. The code implementation is similar to the method for modifying the parasitic parameters, the control input is acquired through the get function, and the set _ param function sets the element parameters.
V＝get(handles.edit9,'String')；
set_param('diancimodel/Constant','Value',V)；
Sequence_signal_F＝get(handles.edit10,'String')；
carrier_f＝get(handles.edit10,'String')；
The operation of the voltage source control signal as a square wave is shown in fig. 5.
Setting the duty ratio of a PWM wave interference voltage source:
the function of changing the duty cycle is realized by changing the size of a constant module compared with the triangular carrier wave, when a constant waveform is taken to be larger than the triangular carrier wave, the voltage source has output, and the duty cycle is increased along with the constant waveform.
The method comprises the steps of representing duty ratio by applying a slider control, setting the range of the duty ratio to be 1-0, linking a slider and a text box, and writing codes into a slider callback function
input＝get(hObject,'Value')；
set(handles.edit12,'String',num2str(input))；
In the PWM simulation model, the triangular carrier signal is moved up to a position above a zero scale, so that the actual value range of the constant module is 0-2, and the corresponding relation between the constant module and the duty ratio is 2: 1, the data needs to be multiplied in the software
ratechu2＝get(handles.edit12,'String')；
rate＝num2str(str2double(ratechu2)*2)；
set_param('diancimodel/Constant2','Value',rate)
The operation of the voltage source control signal as a PWM wave is shown in fig. 6.
Setting the edge gradient and frequency of a trapezoidal wave interference voltage source:
when the signal frequency band is larger than 10MHz, the interference time domain waveform of the chopper circuit can be considered to be approximate to trapezoidal wave due to the need of considering the switching transient interference. In this case, the user needs to adjust parameters such as the switching speed and the edge steepness of the switching device of the chopper circuit according to the user's own needs.
A cyclic sequence module is used in the Simulink model, and a time axis and a parameter axis are reasonably arranged to represent a trapezoidal wave. And finding out the corresponding relation between the edge slope and the frequency and the time parameter in the module, and after the input of the GUI control is obtained, calculating the module parameter and transmitting the module parameter to the simulation element.
It is noted that if the IGBT edge slope parameter is much lower than the switching frequency, an extreme case may occur where the time domain waveform period is less than the time required for the rising edge, and the interface will throw an exception and re-enter the prompt.
The operation of the voltage source control signal as a trapezoidal wave is shown in fig. 7.
Comparison and analysis of prediction results in the invention:
the simulation circuit used by the software is utilized to carry out the physical experiment work of the simplest model, in the example, the direct current source size, the IGBT control signal frequency and the RLC circuit parameters are respectively Udc＝185，f＝185Hz，R1/2＝25Ω，L2//3＝1.724μH，Cmp＝800pF。
The interference source control mode is PWM wave, under the condition that the duty ratio is 50%, the voltage frequency spectrum is the same as that of square wave in the interference source control mode, and the experimental graph is compared. In order to ensure the clarity and accuracy of the simulation result, necessary setting is needed for image drawing. The software prediction result uses the drawing editing function of MATLAB software, the time axis of the software time domain simulation result is converted into time domain and frequency domain, the logarithmic scale is changed, and the prediction signal channel interval and the frequency spectrum interval of the simulation image are set in the same way. The software predicted image is derived as shown in fig. 8, and the common mode spectrum given by the experiment is shown in fig. 9.
Comparing the experimental results, it is found that the software prediction results are very similar to the amplitude and waveform envelope of the experimental images of the examples, however, the horizontal axes of the two images are slightly different, and the frequency positions of the maximum value and the minimum value of the interference voltage are different. Or systematic errors due to differences in fourier transform algorithms. Generally speaking, the comparison of the experimental results is in line with expectations. The scientificity and accuracy of the prediction software are proved, and meanwhile, the correctness of the sensitivity simplification thought is indirectly proved.
Taking the square wave interference source as an example, the circuit output voltage amplitudes are set to be 15, 150 and 1500V respectively, when the voltage output amplitude is increased by 10 times, the current common mode interference voltage is increased by more than 10 times, so that the expected voltage spectrum amplitude increase is more than 20V, and the influence on the image envelope is small. The amplitude voltage spectrum pairs, as shown in fig. 10, increase the image disturbance amplitudes by 20 or more, respectively, in accordance with the expected theory.
The invention and its embodiments have been described above, without limitation, and what is shown in the drawings is only one of the embodiments of the invention and is not actually limited thereto. In summary, those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiments as a basis for designing or modifying other structures for carrying out the same purposes of the present invention without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (9)
1. The BUCK chopper electromagnetic interference prediction software is characterized by comprising the following steps:
selecting and determining a simulation interference model corresponding to the interference source model through interlocked radio buttons;
acquiring a simulation file according to the selected simulation interference model;
if the acquisition of the simulation file fails, an error is reported, and the program is terminated;
if the simulation file is successfully acquired, loading the file for pre-operation; determining a conduction path for distinguishing choppers of different models by inputting parasitic parameters respectively corresponding to element data in the simulation interference model;
setting circuit performance index data corresponding to the chopper in the previous step, wherein the circuit performance index data correspond to different simulation interference models and present different parameters;
judging whether the input circuit performance index data meets the general rule of the corresponding simulation interference model, if not, the data is abnormal, and executing re-input;
if the data are in accordance with the set _ param function, the data are normal, and the data are correspondingly written into the simulation file through the set _ param function and the simulation is run;
displaying a time domain image and a frequency domain image of the predicted common-mode interference voltage through the common-mode interference amplitude value, the maximum value and the resonance point of the target chopper in the simulation result;
if the data needs to be changed for a plurality of times of experiments, re-input is executed, and if the program needs to be ended, a termination program is executed.
2. The BUCK chopper electromagnetic interference prediction software of claim 1, wherein: the simulation interference model comprises three types, namely a square wave, a Pulse Width Modulation (PWM) wave capable of changing duty ratio and a trapezoidal wave capable of changing edge gradient; the simulation interference model consists of basic circuit elements and control signals; the basic circuit elements comprise a resistor, an inductor, a capacitor and an ideal voltage source; the ideal voltage source is used for simulating an actual interference source, namely a circuit output end controlled by a switching device IGBT in the chopper circuit; and the control signal waveform is built through a signal generation module.
3. The BUCK chopper electromagnetic interference prediction software of claim 1, wherein: the parasitic parameters include R, L, C, where R represents the resistance of the impedance stabilization network, L represents the parallel value of the positive and negative bus inductances, and C represents the parasitic capacitance of the IGBT to ground.
4. The BUCK chopper electromagnetic interference prediction software of claim 3, wherein: the calculation formula of the positive and negative bus inductance parallel value L is as follows:
wherein l is the length, w is the width, and t is the height.
5. The BUCK chopper electromagnetic interference prediction software of claim 3, wherein: the calculation formula of the IGBT to ground parasitic capacitance C is as follows:
C＝ε0εγA/d，
wherein A is the surface area and d is the width.
6. The BUCK chopper electromagnetic interference prediction software of claim 1, wherein: in the simulation interference model under the control of the square wave, a square wave generator Signal generator is adopted to control a voltage source; the adjustable circuit performance index data comprises voltage amplitude and waveform frequency, and the steepness of the edge of the IGBT is invariably infinite.
7. The BUCK chopper electromagnetic interference prediction software as claimed in claim 1, wherein: in the simulation interference model under the control of the PWM wave, the opening time is changed under the condition of inconvenient waveform period; the PWM control signal is modulated by a triangular carrier and a Constant module Constant, and a control signal is output to a voltage source by comparing the triangular carrier and the Constant module Constant; the duty ratio of the output waveform of the voltage source is changed by changing the amplitude of the constant module; multiplying the output voltage amplitude and the output result of the comparison unit to change the output amplitude of the interference source; the adjustable circuit performance index data comprise voltage amplitude, frequency and duty ratio and are used for researching the influence of the duty ratio of the circuit switching device control signal on common-mode interference voltage.
8. The BUCK chopper electromagnetic interference prediction software of claim 1, wherein: in the simulation interference model under the control of the trapezoidal wave, finishing the generation of the waveform through a Repeating Sequence module, and realizing the modification of the steepness of the rising edge or the falling edge; the adjustable circuit performance index data comprises a voltage amplitude, a waveform frequency and IGBT edge steepness.
9. The BUCK chopper electromagnetic interference prediction software of claim 1, wherein: obtaining data of the time domain signal through a measuring instrument and a system clock of common mode voltage on an LISN resistor of a simulation interference model; the frequency domain data is obtained by processing the time domain signal through Fourier transform.
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